Various reinforcement fibers and their use in a wide variety of applications are known in the art. For example, it is known to add reinforcement fibers to building materials, such as, asphalt cement concrete and the like, to add strength, toughness, and durability, and to improve the integrity of the asphalt properties. In some applications, reinforcement fibers are added to asphalt to reduce or prevent cracks. Typical reinforcement fibers include asbestos fibers, glass fibers, steel fibers, mineral fibers, natural fibers, synthetic fibers, such as polymer and aramid fibers, and cellulose fibers. Some reinforcement fibers are better suited for particular applications than others. For example, asbestos fibers are known to provide effective reinforcement but, due to environmental and health concerns, these fibers are not extensively used. In addition, some fibers are relatively expensive and therefore, not practical for all applications.
Reinforcement fibers are incorporated into the building materials, such as, asphalt cement concrete, using a variety of conventional methods and techniques. For example, it is known to add reinforcement fibers to an asphalt cement concrete composition during the manufacturing process prior to field placement. For example, in a batch process wherein a mixing machine is used to produce asphalt, reinforcement fibers are added to a mixing chamber having mixing blades, with other ingredients. In a continuous process that uses a drum mixer, the reinforcement fibers are added to the drum mixer. The reinforcement fibers may be added to equipment other than the mixing chamber and the drum mixer. In general, the reinforcement fibers may be added to any associated machinery positioned either before or after the mixing machine or the drum mixer provided that the machinery has the capability to provide sufficient mixing and dispersion of the reinforcement fibers in the asphalt composition. In some instances, the reinforcement fibers are added prior to introducing the liquid asphalt. In other instances, such as, for micro-surfacing and slurry seal, the reinforcement fibers are added simultaneously with other ingredients in the asphalt mixture.
The reinforcement fibers are added to a cement concrete composition either individually or in a bundle or in a container, e.g., bag, coating or the like. Generally, it is advantageous for the reinforcement fibers to be added in a manner that is effective to reduce or minimize entanglement and clumping, and to improve or maximize distribution throughout the composition.
Further, reinforcement fibers can be added to an asphalt cement concrete composition in varying amounts. Typically, the amount added is such that desired properties of the reinforced asphalt are achieved upon field placement.
There is a continuous desire and need in the art to improve the ability of reinforcement fibers to disperse uniformly within an asphalt cement concrete composition, as well, as the ability to provide improved strength, toughness and durability to cement concrete when it is field placed. For example, there is a desire to provide reinforcement fibers that have elastic or stretchable properties that are capable to improve the strength, toughness and durability, and essentially to provide a self-healing property, to field placed asphalt cement concrete.
It is recognized in the asphalt cement concrete industry that there are cracking problems associated with micro-surfacing (MS), which consists of applying a layer of new pavement over existing pavement. Cracking in the MS layer can occur within only months following its placement. There is a need for a more flexible, non-cracking MS treatment, however, there is also a concern that if the MS is too soft, it will rut. Thus, the elastomeric polymer reinforcing fibers of the invention are capable of retarding crack propagation and promoting self-healing to extend pavement life in conventional MS or can be designed with softer binder to reduce rut potential. Reducing cracks in the MS layer can prevent water intrusion, which is known to cause significant damage to highways.